This invention is concerned with control systems for the protection of internal combustion engines.
The need to protect internal combustion engines from damaging or destructive operating conditions is clear. Continued operation of an engine under critical low oil or low coolant conditions can lead to a catastrophic failure of the engine. Fluid monitoring and protection systems are used on engines to discourage operation of the engine when the operating conditions exceed acceptable limits. In the past, various systems of varying degrees of sophistication have been developed to monitor critical fluid conditions in the engine and to implement an engine protection protocol.
In perhaps the simplest such system, an analog gauge signals the advent of an unacceptable engine fluid condition--for instance, the low oil light. Driver warning systems of this type do not provide an ongoing indication of the development of an engine problem until the warning is issued. Analog or digital gauges provide continuous readings of fluid levels and temperatures, but require constant monitoring by the driver. Moreover, these systems provide no history of the engine fluid problems for analysis by those responsible for engine maintenance. More significantly, neither of these approaches automatically implement an engine protection protocol, relying instead on the driver to instinctively recognize the problem and take corrective or protective measures.
Aftermarket retrofit systems have been available that electronically monitor certain engine operating parameters. In some of these systems, the engine is automatically shut down when a critical engine operating parameter is exceeded. While engine shut-down is an effective way to prevent further damage to the engine, this approach greatly reduces the driver's ability to control the vehicle.
Automatic and continuous engine monitoring and control has been made more practical and efficient with the advent of electronics into the automotive and engine markets. The "PEEC" system of Caterpillar, the Detroit Diesel "DDECII" system, and the Cummins Electronics "CELECT" system are current examples of electronic engine controls that continuously monitor and control the operation of an internal combustion engine. Until now, these electronic control systems have relied upon engine shut-down or fixed power cut-back for engine protection. In the former case, the engine is gradually but rapidly shut down through control of an electronic fuel valve. In the latter case, the available engine power is reduced across the entire operating range of the engine. This is achieved by limiting the maximum engine speed, such as in the Caterpillar "PEEC" system, or by limiting the percent available throttle, as in the Detroit Diesel system.
Each of the prior systems do provide absolute protection for the engine - that is, the engine is shut-down when a failure is detected. However, a need exists for an engine protection system that is "smarter", that can modify the engine operation to not only protect the engine but permit continued controlled operation of the engine. There is also a need for a system that can provide a history of engine fluid parameter fault conditions for diagnosis by maintenance personnel.